Despite the fact that fresh fruit and vegetables have been preserved by many methods, the systems which have been developed to date all tend to result in a loss of freshness during processing or a loss of freshness after a short period of storage. In addition, the texture and flavour of the fruits and vegetables which are preserved by present methods is also significantly changed.
It is well known to refrigerate or freeze fruit and vegetables in an attempt to prolong storage life of these products. It is also well known to use hermatic seal film, bags, packages or containers, with or without inert gases, to increase the storage life of fresh fruit and vegetables. In addition, attempts have been made to increase storage life by subjecting the fruits and vegetables to irradiation. While each of these techniques provides an improvment over the mere storing of the fruits and vegetables at ambient temperature, the systems have serious limitations whether used individually or in combination.
Some fruits such as papaya and mango and the like cannot be frozen without destroying the texture and flavour. Furthermore, without the deactivation of enzymes, ethylene gas is produced and the flavour and texture of the products deteriorates rapidly, even when refrigerated. Radapperation has proven to be the most effective long range chemical free way of preseving food such as fruit and vegetables. In this process, the fruits and vegetables are cooked and are then placed in a hermatic sealed container which is then sterilized by an irradiation process. This process is not suitable for fresh fruit or vegetable preservation because the texture and the flavour is destroyed.
Enzymes are a group of proteins found in living plant cells which catalyze a variety of chemical reactions. Over one thousand such enzymes have been discovered in fruits and vegetables. When fruits and vegetables are harvested, it is normal for senescence to set in. During this period ethylene gas is formed within the fruit or vegetables. This gas triggers the activation of the enzymes, e.g. breakdown of pectin, protein, etc., which causes a breakdown of the fruit or vegetables.
Enzymes are deactivated by heat to coagulate or denature at temperatures over 50.degree. C.
The freshness, texture and flavour of many fruits and vegetables will be adversely affected if the fruit or vegetable is held at the enzyme deactivating temperature beyond a critical dwell time which varies with different fruits or vegetables. Generally if a fruit or vegetable is heated to a temperature of 90.degree. C. and is held at this temperature for ten minutes, the naturally occurring enzymes will be deactivated.
It is known that fruits and vegetables can be damaged if subjected to excessive irradation and consequently it is desirable to minimize the radiation dosage used for the purpose of sterilizing fruits and vegetables.
Research and reports from medical authorities show that many people are allergic to sulphur dioxide. Sickness and death have resulted from consumption of sulphur dioxide. Sulphur dioxide is used in fruit and vegetable salads, dried fruits, etc. to retain freshness, colour and to partially preserve.
The present process allows cut fruits and vegetables, e.g. fresh fruit salad and fresh vegetable salad to be prepared, hold and eaten without the need to use sulphur dioxide as a preservative.